Initial Phosphate Concentration Research Articles

Development of polyaminated chitosan-zirconium(IV) complex bead adsorbent for highly efficient removal and recovery of phosphorus in aqueous solutions

The aim of this work is to examine the adsorption performance and mechanism of phosphorus (P) onto polyethyene polyamine (PEPA) grafted chitosan-zirconium(IV) composite beads (CS-Zr-PEPA) from aqueous solutions. The morphology, functional groups, and surface area of the CS-Zr-PEPA beads were characterized by SEM, FTIR, and BET analysis. Batch adsorption experiments were conducted via different operating parameters such as solution pH, initial phosphate concentration, co-existing anions and temperature. The adsorption kinetics, equilibrium isotherms and adsorption stability of the adsorbent were scrutinized. In comparison with other CS-based beads, the CS-Zr-PEPA had a greater affinity towards P and exhibited a maximum adsorption capacity of 103.96 mg-P/g predicted by Langmuir mode. The reusability studies of CS-Zr-PEPA beads were carried out. The CS-Zr-PEPA beads exhibit preferable sequestration of P through specific interactions, as further demonstrated by studying physicochemical characteristics of the virgin beads and P-adsorbed beads using X-ray photoelectron spectroscopy (XPS). The column performance of CS-Zr-PEPA beads was tested with P-containing wastewater. Results indicated that the developed CS-Zr-PEPA composite beads could be utilized as a promising adsorbent for effective removal and recovery of P from water and wastewater.

Recyclable adsorbents based on Fe3O4 nanoparticles on lanthanum-modified montmorillonite for the efficient phosphate removal.

Montmorillonite (MMT) clay modified with lanthanum (La) ions and Fe3O4 nanoparticles was proposed for the effective removal of phosphate ions from aqueous solution. Characterisation of the adsorbent using FTIR, SEM, XRD, XPS, XRF, BET and VSM techniques were carried out. The effects of initial phosphate concentration, contact time, dosage and pH on the phosphorus adsorption were investigated. La-MMT/Fe3O4 exhibited an excellent adsorption capacity of up to 14.35 mg/g, with 97.8% removal within 60 min. Langmuir isotherm model fits well with the equilibrium isotherm data, with a maximum adsorption capacity of 15.53 mg/g at room temperature. The kinetic study was well fitted with pseudo-second-order kinetics, and the adsorption rate was mainly controlled by liquid-film diffusion. The manufactured adsorbent was effectively regenerated using 0.1 M NaOH solutions, with 90.18% adsorption efficiency remaining after six adsorption/desorption cycles. These results demonstrate that La-MMT/Fe3O4 provides an example of regenerable high-performance adsorbents for removal of PO43- from wastewater.

Benign zinc oxide betaine-modified biochar nanocomposites for phosphate removal from aqueous solutions

Phosphate is one of the most costly and complex environmental pollutants that leads to eutrophication, which decreases water quality and access to clean water. Among different adsorbents, biochar is one of the promising adsorbents for phosphate removal as well as heavy metal removal from an aqueous solution. In this study, biochar was impregnated with nano zinc oxide in the presence of glycine betaine. The Zinc Oxide Betaine-Modified Biochar Nanocomposites (ZnOBBNC) proved to be an excellent adsorbent for the removal of phosphate, exhibiting a maximum adsorption capacity of phosphate (265.5 mg. g−1) and fast adsorption kinetics (~100% removal at 15 min at 10 mg. L−1 phosphate and 3 g. L−1 nanocomposite dosage) in phosphate solution. The synthesis of these benign ZnOBBNC involves a process that is eco-friendly and economically feasible. From material characterization, we found that the ZnOBBNC has ~20–30 nm particle size, high surface area (100.01 m2. g−1), microporous (25.79 Å) structures, and 7.64% zinc content. The influence of pH (2–10), coexisting anions (Cl−, CO32−, NO3− and SO43−), initial phosphate concentration (10–500 mg. L−1), and ZnOBBNC dosage (0.5–5 g. L−1) were investigated in batch experiments. From the adsorption isotherms data, the adsorption of phosphate using ZnOBBNC followed Langmuir isotherm (R2 = 0.9616), confirming the mono-layered adsorption mechanism. The kinetic studies showed that the phosphate adsorption using ZnOBBNC followed the pseudo-second-order model (R2 = 1.0000), confirming the chemisorption adsorption mechanism with inner-sphere complexion. Our results demonstrated ZnOBBNC as a suitable, competitive candidate for phosphate removal from both mock lab-prepared and real field-collected wastewater samples when compared to commercial nanocomposites.

Removal of phosphate at low concentration from water by porous PVA/Al2O3 composites

ABSTRACT The porous polyvinyl alcohol (PVA)/Al2O3 composite by supporting activated alumina on the cross-linked network of PVA has been successfully prepared and its property for the removal of phosphate in aqueous solution was also evaluated. The structure of the PVA/Al2O3 was examined by scanning electron microscopy. It showed that the activated alumina particles with an average size of 1 μm were evenly dispersed and fixed in the cross-linked network structure of PVA. The effects of adsorption time, solution temperature, pH, initial concentration of phosphate, Al2O3 loading rate, dosage and coexisting ions on the phosphate removal were further studied. The results showed that the highest removal phosphate efficiency of 95% can be obtained with the Al2O3 loading rate of PVA/Al2O3 being 60 wt.% at pH of 4 at 30 °C. The maximum adsorption capacities of by PVA/Al2O3 suggested by the Langmuir isothermal model was 10.12 mg/g. The adsorption process of phosphate can be fit well with a pseudo-second-order model (R 2 = 0.9900). The PVA/Al2O3 composite exhibited a high selective adsorption of phosphate in the presence of commonly coexisting anions except the obvious effect of in water. Meanwhile, the PVA/Al2O3 composite can be easily separated and recovered due to the granulation of adsorbent. PVA/Al2O3 composite also shows the excellent properties of regeneration and recycling use with the removal efficiency of phosphate was 88.93%, 88.38% and 94.34% after three cycles, respectively. It can be proposed that the PVA/Al2O3 composite is a promising recyclable adsorbent for removing phosphate at low concentration from aqueous solution.

Simultaneous Removal of Arsenate and Chromate from Ground- and Surface- Waters by Iron-Based Redox Assisted Coagulation

Arsenic (As) and chromate (Cr(VI)) contamination of ground and surface waters is a major problem worldwide. Given that a new drinking water limit is anticipated for Cr(VI) and that the limit of arsenic in drinking water is quite low (10 μg/L), there is an urgent need for evaluating technologies that could be efficient for removal of both contaminants simultaneously. In this work, the use of Fe(II) redox assisted coagulation was investigated to simultaneously remove the contaminants of interest. The basic principle of this technology is that Fe(II) could react with Cr(VI) and form Fe(III)-hydroxides and insoluble Cr(III) species, while the freshly formed Fe(III) hydroxides are very efficient adsorbents for As(V). The effect of pH, the water matrix composition, Fe(II) dose, initial contaminant concentrations, NOM presence and phosphate concentration were the examined parameters. The results revealed that with a dose of 2 mg/L Fe(II), residual As(V) and Cr(VI) concentrations were both below 10 μg/L, from initial concentrations of 50 μg/L. Though, this is effective only at circumneutral pH values. This is however not a big obstacle, since most natural waters, especially groundwaters, have near neutral pH values. At these pH values, residual iron concentration was far below 200 μg/L. The presence of phosphate anions inhibited As(V) removal but had no effect on Cr(VI) removal. Increasing Fe(II) concentrations eliminated the effect of phosphate and provided simultaneous phosphate removal. Therefore, Fe(II) coagulation can be applied, with secured results, for simultaneous As(V), Cr(VI) and phosphate removal from waters.

Pilot-scale cultivation of Chlorella sorokiniana FZU60 with a mixotrophy/photoautotrophy two-stage strategy for efficient lutein production

Chlorella sorokiniana FZU60, a lutein-enriching microalga, was cultivated in 50 L column photobioreactor to evaluate its potential for lutein production. Initial cell concentration, phosphate concentration and aeration rate were optimized, and results showed that optimal conditions of these three parameters were 0.10 g/L, 0.06 g/L and 0.02 vvm (2.5% CO2), respectively. In addition, a novel two-stage strategy was successfully developed, in which algae were firstly cultivated under fed-batch mixotrophic condition to achieve high biomass concentration, and then shifted to photoautotrophic condition for enhancing lutein accumulation. Moreover, dissolved oxygen was found to be an efficient indicator of acetate depletion in fed-batch stage. The obtained lutein content, production and productivity reached 9.51 mg/g, 33.55 mg/L and 4.67 mg/L/d, respectively, which were greater than those reported in other pilot-scale studies. This proposed strategy provided a cost-effective approach for high-efficient microalgae-based lutein production at pilot-scale, indicating great potential for commercial production.

CHARACTERIZATION AND EFFECTIVENESS OF MORINGA OLEIFERA SEEDS EXTRACT AS A PHOSPHATE COAGULANT

In this research, Moringa oleifera seeds extract has been shown the ability as a coagulation agent. The molecules that act as the coagulation agents were the proteins which were obtained by the extraction process of the Moringa seeds using NaCl solution. The aim of this research was to characterize and test the effectiveness of the Moringa seeds extract as a phosphate coagulant. The determination of the coagulation process was carried out using a Jar Test method of phosphate solution samples, and then effectiveness the samples were analyzed using a UV-Vis spectroscopy after-treatment of the coagulant dose variations, depositional time, and the pH variations of the samples. The characterization of the extract functional groups was determined using an FTIR spectroscopy. The results of the coagulation phosphate sample examinations showed that the optimum dose of the coagulant was 80 mL/L, with a decrease in the initial phosphate concentration of 17 ppm to 13.58 ppm. The reduction effect of precipitation time and pH also was obtained in this research. The optimum precipitation time and pH were in 30 minutes and pH 8, which reduced the phosphate concentration to 11.697 and 9.6 ppm, respectively. The FTIR spectra of Moringa oleifera seeds extracts before and after interacting with phosphate showed their differences. The interactions between the extract and phosphate were demonstrated by the appearance of buckling vibrations at wavenumbers 1064.2 cm-1, 799.8 cm-1, and 668.8 cm-1. The results of this study indicated that the Moringa seeds extraction with NaCl has potential as a phosphate coagulation agent.

High concentration phosphate removal by calcite and its subsequent utilization for tetracycline removal

The excess phosphate and tetracycline (TC) in natural environments potentially threatens ecosystem. Few studies were conducted on efficient and cost-effective method for dealing with these pollutants together. we attempted to reutilize this abandoned calcite for the removal of other pollutant in wastewater, such as tetracycline. Firstly, removal of high concentration phosphate by calcite was studied in batch experiments. Thereafter, removal of TC by this used calcite (P-loaded calcite) was investigated under different conditions: pH, phosphate concentration, dried state and humid state. Using calcite for high concentration phosphate removal, the results showed that (1) concentrations of phosphate higher than 30 mg.L−1, resulted in a significant phosphate precipitation on calcite surface at both pH7.7 and pH 8.3 within 24 h. The corresponding pH and calcium results confirmed this precipitation occurrence; (2) the precipitated phase was supposed to be amorphous calcium phosphate through the results of IR, XPS, XRD and BET analysis. Compared to that by pure calcite, the TC removal rate by P-loaded calcite increased significantly with the initial phosphate concentration in both cases of Humid Experiment and Dried Experiment. This may be attributed to the adsorption of TC on the precipitated amorphous calcium phosphate, which has a larger specific surface and increasingly generates > Ca+ sites. From the similarity of TC removal rate by P-loaded calcite between pH7.7 and pH 8.3, it is hypothesized that TC removal is due to TCH2° and TCH- adsorption on > Ca+ sites. The minor difference of TC removal rate by P-loaded calcites between Humid Experiment and Dried Experiment is mainly due to slight dissolution of precipitated amorphous calcium phosphate. Our research will serve as reference knowledge for the reutilization of abandoned calcite in phosphate removal, which provides a new way to reduce the wasted materials and environmental risks induced by tetracycline.

Synthesis of nanoZrO2 via simple new green routes and its effective application as adsorbent in phosphate remediation of water with or without immobilization in Al-alginate beads.

Nano particles of ZrO2 of average size 10.91 nm are successfully synthesized via green routes from a solvent blend of water and ethylene glycol (4:1 v/v). Bio-extract of seeds of Sapindus plant is employed as stabilizing and/or capping agent and homogeneous method of precipitation is adopted to generate the precipitating agent. The nZrO2 particles are immobilized in aluminum alginate beads (nZrO2-Al- alig). Nano-ZrO2 and beads are investigated as adsorbents for the extraction of phosphate from water. The controlling physicochemical parameters are studied for the maximum phosphate removal using simulate water. The optimum conditions are: pH: 7; sorbent dosage: 0.1 g/100 mL for nZrO2 and 0.08 g/100 mL for beads; equilibration time: 30 min.for nZrO2 and 35 min for beads; initial phosphate concentration: 50 mg/L; temperature: 30 ± 1 °C; 300 rpm. The adsorption capacities are: 126.2 mg/g for nZrO2 and 173.0 mg/g for 'nZrO2-Al- alig' and they are higher than many reported in literature. The beads, besides facilitating the easy filtration, are exhibiting enhanced cumulative phosphate-adsorption nature of nanoZrO2 and Al-alginate. X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray (EDX) investigations are employed in characterizing the adsorbents. Of the various isotherm models analyzed to assess the nature of adsorption, Freundlich model provides the best correlation (R2 = 0.99 for nZrO2 and R2 = 0.99 for 'nZrO2-Al-alig'), indicating the heterogeneous and multi-layered adsorption process. Thermodynamic studies reveal the endothermic and spontaneous nature of sorption. Pseudo-second-order model of kinetics describes the adsorption well. Spent adsorbents can be regenerated with marginal loss of adsorption capacity until five cycles. The sorbents are successfully applied to remove phosphate from polluted lake water samples.

Kinetics, Isotherms, and Thermodynamic Modeling of the Adsorption of Phosphates from Model Wastewater Using Recycled Brick Waste

Phosphates in wastewater at elevated concentrations cause eutrophication of water bodies and their removal from treated wastewater is essential before effluents are discharged to the environment. Phosphates are predominately removed during wastewater treatment by chemical precipitation which is usually expensive and has a significant environmental footprint. The purpose of this study was to investigate the effectiveness of waste recycled bricks as adsorbent for phosphate removal during wastewater treatment. The kinetics, isotherms, and thermodynamics of adsorption were investigated to establish the mechanisms of adsorption. The results showed that adsorption capacities increased with an increase in contact time, adsorbent dosage, and initial phosphate concentration. The kinetic study indicated that adsorption was governed by several mechanisms with various processes dominating different stages of the adsorption. The adsorption process was better represented by the pseudo-second-order kinetics and the Langmuir isotherm adequately described the adsorption of phosphates onto brick particles with a maximum adsorption capacity of 5.35 mg/g. The thermodynamic studies showed that the adsorption process was exothermic and proceeded spontaneously, demonstrating that waste bricks can be used as a sustainable alternative for the effective removal of phosphates from wastewater.

Removal of inorganic and organic phosphorus compounds from aqueous solution by ferrihydrite decoration onto graphene.

Existing research on phosphorus removal from wastewater mostly focused on inorganic phosphorus while ignoring organic phosphorus, which has potential bioavailability. This study aims to provide an innovation for the development of advanced treatment material for both inorganic and organic phosphorus removal in water. In this study, ferrihydrite loaded on the graphene oxide (FeOOH-GO) composite adsorbent was synthesized by surface precipitation method, and its ability to remove both phosphate and diazinon as forms of inorganic and organic phosphorous from water was investigated. Characterization of the loaded composite using X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier transform-infrared spectroscopy (FTIR) indicated that FeOOH was successfully loaded onto graphene. The results of batch adsorption experiments showed that the adsorbent could remove both inorganic and organic phosphorus compounds simultaneously from water. When FeOOH content is 40%, the equilibrium adsorption amount of FeOOH-GO composite adsorbent for phosphate and diazinon was 5.81 and 23.20mgg-1, respectively. Environmental parameters such as pH and initial concentration have important influence on phosphorus removal by FeOOH-GO composite adsorbent and the removal efficiency of the inorganic and organic phosphorus from water decreases by increasing the initial concentration of phosphate and diazinon and the pH. It was concluded that the FeOOH-GO composite adsorbent has great potential to remove both inorganic and organic phosphate simultaneously from contaminated water.

Removal of Phosphate Ions from Aqueous Solutions by Adsorption onto Leftover Coal

High loadings of wastewater with phosphors (P) require purification measures, which can be challenging to realize in regions where the technical and financial frame does not allow sophisticated applications. Simple percolation devices employing various kinds of adsorbents might be an alternative. Here, we investigated the application of leftover coal, which was collected from Ethiopian coal mining areas, as an adsorbent for the removal of phosphate from aqueous solutions in a classical slurry batch set-up. The combined effects of operational parameters such as contact time, initial concentration, and solution pH on P retention efficiency was studied employing the Response Surface Methodology (RSM). The maximum phosphate adsorption (79% removal and 198 mg kg−1 leftover coal) was obtained at a contact time of 200 min, an initial phosphate concentration of 5 mg/L, and a solution pH of 2.3. The Freundlich isotherm was fitted to the experimental data. The pseudo second-order equation describes the experimental data well, with a correlation value of R2 = 0.99. The effect of temperature on the adsorption reveals that the process is exothermic. The results demonstrate that leftover coal material could potentially be applied for the removal of phosphate from aqueous media, but additional testing in a flow-through set-up using real wastewater is required to draw definite conclusions.

Preparation, Characterization, and Application of Novel Ferric Oxide-Amine Material for Removal of Nitrate and Phosphate in Water

Ferric oxide-amine material was synthesized and applied as a novel adsorbent for nitrate and phosphate removal from aqueous solution. The properties of ferric oxide-amine were examined using TGA, FTIR, BET, SEM, EDX, SEM-mapping, and XRD analysis. The results showed that the adsorption using ferric oxide-amine material reached equilibrium after 30 and 60 min for nitrate and phosphate, respectively. The highest nitrate and phosphate adsorption capacities were 131.4 mg nitrate/g at pH 5-6 and 42.1 mg phosphate/g at pH 6. The effects of adsorbent dosage, initial concentrations of nitrate and phosphate, and adsorption temperature were also investigated. Among the three adsorbents of ferric oxide-amine, ferric oxide, and Akualite A420 ion exchange resin, ferric oxide-amine material had the highest adsorption capacity for nitrate and phosphate removal. These results suggest a great potential use of ferric oxide-amine material for water treatment in practical applications.

Moderate to severe hyperphosphataemia as an independent prognostic factor for 28-day mortality in adult patients with sepsis

BackgroundIschaemic tissue injury caused by tissue hypoperfusion is one of the major consequences of sepsis. Phosphate concentrations are elevated in ischaemic tissue injury. This study was performed to investigate the...

An Improved Natural Transformation Protocol for the Cyanobacterium Synechocystis sp. PCC 6803

The naturally transformable cyanobacterium Synechocystis sp. PCC 6803 is a widely used chassis strain for the photosynthetic production of chemicals. However, Synechocystis possesses multiple genome copies per cell which means that segregating mutations across all genome copies can be time-consuming. Here we use flow cytometry in combination with DNA staining to investigate the effect of phosphate deprivation on the genome copy number of the glucose-tolerant GT-P sub-strain of Synechocystis 6803. Like the PCC 6803 wild type strain, the ploidy of GT-P cells grown in BG-11 medium is growth phase dependent with an average genome copy number of 6.05 ± 0.27 in early growth (OD740 = 0.1) decreasing to 2.49 ± 0.11 in late stationary phase (OD740 = 7). We show that a 10-fold reduction in the initial phosphate concentration of the BG-11 growth medium reduces the average genome copy number of GT-P cells from 4.51 ± 0.20 to 2.94 ± 0.13 and increases the proportion of monoploid cells from 0 to 6% after 7 days of growth. In addition, we also show that the DnaA protein, which unusually for bacteria is not required for DNA replication in Synechocystis, plays a role in restoring polyploidy upon subsequent phosphate supplementation. Based on these observations, we have developed an alternative natural transformation protocol involving phosphate depletion that decreases the time required to obtain fully segregated mutants.

Optimum Operating Conditions for the Removal of Phosphate from Water Using of Wood-Branch Nanoparticles from Eucalyptus camaldulensis.

A batch bio-sorption experiment was conducted on Eucalyptus camaldulensis Dehnh. wood-branch in the form of woody sawdust nanoparticles (nSD-KF) to evaluate their potential efficiency as phosphate bio-sorption capacity. The operating parameters of phosphate bio-sorption including contact time, initial concentration, pH, temperature, dosage, size, competing ion, and the possible mechanisms responsible for phosphate removal from water were investigated. The nSD-KF were green-synthesized by ball mill grinder and phosphate solutions with various concentrations were performed. The results revealed that the maximum adsorption capacity (qmax) value of nSD-KF was 50,000 µg/g. In addition, the removal efficiency of nSD-KF significantly increased with the increase of initial phosphate concentration, contact time, temperature, and dosage. However, it decreased with the increase of pH and in double-system solution with the presence of ammonium ions. At the application study, the nSD-KF successfully removed 87.82% and 92.09% of phosphate from real agricultural wastewater in a batch experiment and in a column experiment, respectively. Adsorption efficiency of nSD-KF for phosphate increased after the first and second regeneration cycles, but it decreased after the third and fourth cycles. The poor to moderate phosphate desorption from nSD-KF sorbent indicates the stability of phosphate bound to nSD-KF materials. Regardless, biodegradability of nSD-KF-loaded phosphate is possible, and it will be a good source of phosphate to a plant when added to the agricultural soil as a supplemental application of fertilizer. In conclusion, nSD-KF could be considered as a promising lignocellulosic biomaterial used for the removal of phosphate from waters as bio-sorption process.

Phosphate Sorption onto Structured Soil

Soil–phosphorus interactions are frequently studied employing the slurry technique, in which soil samples are intensively mixed with phosphate solutions of various concentrations. The result of such experiments is a “phosphate sorption potential” because the thorough mixing of soil and phosphate solution as obtained by overhead or horizontal shaking of the slurry would probably not occur under natural conditions, especially if the soil is structured. Here, we wanted to test the impact of soil structure on phosphorus (P) removal from aqueous solution. Soil aggregates of a defined size class were prepared by carefully sieving the soil. The soil aggregates were individually wrapped in an inert fabric and placed on a sieve, which was lowered into a basin containing a phosphate solution of a given concentration. The decrease of the phosphate solution concentration with time was registered at fixed intervals, and adsorbed amounts were quantified by differences between initial concentrations and concentrations at the time of sampling. Pre-tests on fine earth revealed that sorption was more pronounced in the classical slurry batch experiment than in the approach used in this study. Differences between methods were more pronounced at lower initial phosphate concentrations. The increase in P sorption in the classical batch experiment continued over 24 h to 140 mg kg−1, while the adsorbed P amount remained constant (64 mg kg−1) after 6 h in the diffusion experiment. Interestingly, it was observed that the sorption onto soil aggregates was elevated as compared to unstructured fine earth. The sorption capacity of aggregates was approximately one third higher than that of the fine earth samples according to optimized Freundlich adsorption coefficients. This was unexpected since it was assumed that the soil surface area available for sorption processes is greater or at least far more accessible if the unstructured fine earth is exposed to the phosphate solution. We conclude that if the inner pore space of soil aggregates is readily accessible and diffusion is not hindered, the overall retention capacity of intact aggregates might be higher than that of the disturbed soil because the intra-aggregate pore space can accommodate a certain fraction of phosphate in addition to the adsorbed amount at particle surfaces. The presented experimental approach allows for studying sorption processes in well-structured and fine earth in conditions that perform better compared to the natural situation. Additional testing of the method for different soil types is advisable.

La(III)-bentonite/chitosan composite: A new type adsorbent for rapid removal of phosphate from water bodies

It is highly imperative to remove phosphorus from water bodies because the excessive phosphorus content can cause eutrophication of water bodies. In this work, we prepare a kind of environmentally friendly and low-cost adsorbent comprising lanthanum (La)-doped bentonite and chitosan, with a simple, facile and scalable method combining direct calcination and subsequent blending. The optimal adsorbent, La-doped bentonite/chitosan-5, La-BC-5 hereinafter, can rapidly reach equilibrium in 20 min and provide 93.2% adsorption efficiency (initial phosphate concentration, 50 mg/L); and as high as 99.7% could be removed in 5 min under low phosphate concentration (2 mg/L). Fitting result indicates the phosphate adsorption isotherm fits the Freundlich model, meanwhile the adsorptive kinetics follows a pseudo-second-order model. Anti-interference result for some typical anionic species including NO3−, SO42−, Cl−, indicates 97.5% removal efficiency could be achieved under coexisting phosphate concentration of 5 mg/L. Meanwhile, reusability experiment reveals that removal efficiency decreases to 89.1% after five regeneration cycles. Notably, practical water adsorption experiment manifests the La-BC-5 can efficiently reduce the phosphate concentration from 0.30 to 0.07 mg/L. The favorable properties with rapid adsorption, excellent anti-interference for coexisting anions and reusability foresee the enormous potentials for practical phosphate removal in water bodies.

Use of Iron-modified Calcite as an Active Capping Material to Control Phosphorus Release from Sediments in Surface Water Bodies

The use of calcite (CA) as an active capping material has high potential for controlling the release of phosphorus (P) from sediments, but its efficiency still needs to be enhanced. To address this issue, an iron-modified CA (Fe-CA) was prepared, the removal performance of phosphate from aqueous solution by Fe-CA was studied, and the efficiency of the use of Fe-CA as an active capping material to prevent the liberation of P from sediments was investigated. The results showed that Fe-CA exhibited much higher phosphate removal ability than CA. The phosphate removal efficiency of Fe-CA increased with an increase in the Fe-CA dosage. Increasing the initial phosphate concentration gave rise to an increase in the amount of phosphate removed by Fe-CA, and the maximum amount of phosphate removed by Fe-CZ reached 3.09 mg·g-1. Sediment capping with Fe-CA could effectively control the release of soluble reactive P (SRP) from the sediment into the overlying water, leading to a very low concentration of SRP in the overlying water. Additionally, the Fe-CA capping also resulted in the transformation of a small amount of redox-sensitive P (BD-P) and metal-oxide-bound P (NaOH-rP) in sediments to residual P (Res-P), leading to a slight increase in the stability of P in the sediment. The overwhelming majority (90.8%) of P bound by the Fe-CA capping layer existed in the form of NaOH-rP, calcium-bound P (HCl-P), and Res-P, which are relatively very stable. Furthermore, the percentage of bioavailable P (BAP) as a proportion of total extractable P in the P-bound Fe-CA capping layer was very low, and the bound P was re-released with difficulty into the water column for algae growth. Compared to CA capping, the efficiency for the control of sedimentary P release into the overlying water by Fe-CA capping was much higher, and the stability of P bound by the Fe-CA capping layer was also higher. The results of this work indicate that Fe-CA is a very promising active capping material for the interception of the release of P from sediments into the overlying water.

Application of synthesized bovine serum albumin-magnetic iron oxide for phosphate recovery

Phosphorous is an essential nutrient that is widely used as a fertilizer in agriculture. However, its increased discharge from agricultural runoff contributes to eutrophication, necessitating its removal from wastewater. Adsorption is one of several treatment processes for this purpose. In this study, bovine serum albumin-magnetic iron oxide (BSA-MIO) was successfully synthesized using the co-precipitation method. Its morphology was characterized by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. Different parameters that affect adsorption, such as initial phosphate concentration, reaction time, adsorbent dosage, pH, coexisting anions, and temperature, were investigated. The results showed that phosphate adsorption increased with reaction time and temperature while it decreased with an increase in solution pH. The phosphate adsorption equilibrium time using BSA-MIO was 1 h. The estimated maximum adsorption capacity of BSA-MIO was 20.7 mg P·g−1. Moreover, the pseudo-second-order model (R2 > 0.99) and Langmuir model (R2 > 0.99) elucidated the better description of the adsorption kinetics and isotherm, respectively, thereby suggesting the chemisorption nature of adsorption. The coexisting anions (NO3−, Cl−, SO42−, and CO32−) showed no significant effect on phosphate adsorption. Moreover, the adsorbed phosphate was successfully desorbed using different concentrations and combinations of NaOH and NaCl.